On second thought, this is actually a good scheme and could be within the TOS. It is just another form of marketing, as long as the people he hire don't tell their new net friends to click, this should be allowed. I think I'll send an email to get permission, this seems like a cheap and effective marketing method.
Yet another "why did I get banned?" thread in the making. This is not even close to being acceptable, but go ahead, e-mail them, you might just catch a person that just got canned at Google is gives you the go ahead.